A normal human heart pumping pattern is called a sinus rhythm, and is regulated by the body's biological pacemaker within the upper right chamber of the heart, which is commonly referred to as the right atrium. This natural pacemaker, which is generally referred to as the sinoatrial (SA) node, sends electrical signals to the right and left ventricular muscles in the lower chambers of the heart. The ventricular muscles then implement the pumping action under control of the SA node. The right ventricular muscle pumps blood to the lungs for oxygenation, and the left ventricular muscle pumps the oxygenated blood to various parts of the body.
In certain circumstances, the normal or sinus heartbeat rhythm may be adversely affected as a result of some type of malfunction in the heart's electrical control system. When this type of malfunction occurs, an irregular heartbeat may result, causing the ventricular muscles to pump ineffectively, thus reducing the amount of blood pumped to the body. This irregular heartbeat is generally referred to as an arrhythmia.
A particularly serious arrhythmia is known as Ventricular Fibrillation (VF), which is a malfunction characterized by rapid, uncoordinated cardiac movements replacing the normal contractions of the ventricular muscles. In this event, the ventricular muscles are not able to pump blood out of the heart, and there is no initiation of a heartbeat. VF rarely terminates spontaneously, and is therefore a leading cause of sudden cardiac death. The unpredictability of VF and other irregular heat beat conditions exacerbates the problem, and emphasizes the need for early therapeutic intervention to prevent the loss of life.
Defibrillators are devices for providing life-saving electrical shock therapy to persons experiencing an irregular heat beat, such as VF. A defibrillator provides an electrical shock to the heart, in order to convert the irregular heat beat to a normal sinus rhythm. One type of defibrillator is surgically implanted in patients who are considered likely to need electrical shock therapy, precluding the necessity of constant monitoring by medical personnel.
A more commonly used type of defibrillator is the external defibrillator, which sends electrical shock pulses to the patient's heart through external electrodes applied to the patient's chest. External defibrillators may be manually operated, as are typically used in hospitals by medical personnel or may be semiautomatic, semi-automated, fully automatic, or fully automated devices, where they can be used in any location where an unanticipated need may occur.
It is well known that time is an important factor in the successful application of electrical shock therapy. According to recent data, the survival rate of persons suffering from ventricular fibrillation decreases by about ten percent (10%) for each minute the administration of a defibrillation shock is delayed. It is therefore desirable to minimize the time duration between powering up an external defibrillator and administering the electrical shock therapy to the patient.
Prior to delivery of the defibrillation shock, the defibrillator electrodes are attached to the patient, the patient's condition and parameters are measured and analyzed, and a shock energy circuit is charged to an appropriate level. One or more of these activities can be done by medical/emergency personnel, as in the case of manual defibrillators, or by an automatic or automated process, as in the case of automatic, semi-automatic, automated and semi-automated defibrillators. These actions are disadvantageously time-consuming, and delay the administration of the shock therapy.
Accordingly, it is desirable to reduce the inherent time delays associated with shock administration in external defibrillators. In addition, it is desirable to implement delay reductions in all types of external defibrillators, including fully automatic, semi-automatic, fully automated or semi-automated and manual defibrillators. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.